Kiernan Shipka reads to kids from the East Los Angeles Boys & Girls Club during a private event held at The Disney Store on Saturday afternoon (November 16) in Santa Monica, Calif.

The 14-year-old Mad Men star will voice Oona, the mermaid in the upcoming Sofia the First: The Floating Palace primetime special.

Sofia the First: The Floating Palace takes Sofia (Ariel Winter) and her family on an extraordinary journey to Merriway Cove, where Sofia meets a young mermaid named Oona. After helping Oona untangle her fin from a net, Sofia’s magical amulet transforms her into a mermaid too, allowing her to explore the underwater world with her new friend.

During their adventure, Sofia learns that mermaids mistrust humans and are angry that her family’s floating palace is in their cove. When Oona is captured by a horrible sea monster, Sofia – with a little help from Princess Ariel – must find a way to save her and create harmony between their two worlds.